Electrode structure



Dec. 24, 1946. v Q P CHEV|GNY ETAL 2,412,965

ELECTRODE STRUCTURE Filed July 10, 1941 ATTORNEY Patented Dec. 24, 1946 UNITED STATES maar orties- ELECTRODE STRUCTURE Application July 10, 1941, Serial No. 401,740

S Claims.

This invention relates to improvements in electrodes for electron discharge devices, and in particular to improved deflecting electrodes for cathode ray tubes.

It is an object of the invention to provide irnproved means for controlling the magnitude of deflection of a cathode ray beam. f

Another object is to increase the sensitivity of cathode ray devices.

A further object is to provide improved means for controlling the amount of deflection of a cathode ray beam for given applied deflecting potentials.

Other objects and various further features of novelty and invention will hereinafter be pointed out or will become apparent from a reading of the following specification in conjunction with the drawing included herewith. In said drawing- Figs. l and 2 are schematic showings illustrating principles of operation of devices according to the invention, and

Figs. 3 and 4 are partly broken away and partly sectionalized showings of preferred forms of the invention,

When a cathode ray tube is employed as a device for indicating some quantity such as a phase angle, it is customary to set up a circular sweep of the ray by means of quadrature currents applied to the deflection plates and to modulate this sweep radially with a control Voltage 3 proportional to the quantity in question. Such a control voltage may be applied to various electrodes, and as a rule it is applied between a pair of concentric electrodes disposed between the deflecting plates and the screen. These conceni tric electrodes may be of generally conical form and are considered undesirable because they permit only a very limited degree of radial modulation of the beam, and this to such an extent that it is not possible to form a spot near the center of the tube.

It is well known that the extent of radial deflection of a cathode ray depends upon the potential gradient transverse to the beam and upon the distance that the beam must traverse through a field having this gradient. With the known forms of concentric conical electrodes, both electrodes must be relatively closely spaced in order to maintain a uniform control field therebetween. As a result it is only possible to obtain relatively limited radial deflections.

We have found that, by varying the shape of these concentric electrodes whereby a barrelshaped path is prescribed for the electron'beam, it will be possible to provide for radial deflection (Cl. Z50- 158) of the spot extending along any entire radius of the screen. It is thus possible, when desired, to return the beam spot to the center of the screen with each control Voltage impulse.

How such a eld may be set up and its effect upon a pair of electrons may be appreciated by referring to the schematic showing of Fig. 1. In this drawing three relatively short sets of concentric conical electrodes I0, II, I2 illustrate what sort of effect may be expected of the proposed non-conical concentric electrode structure. The beam of electrons I3 may have a normal trajectory sweeping circularly so as to describe a generally circular orbit I4, I5 on the fluorescent screen of the tube. Now the effect of a relatively positive potential on the inner electrode I0' with respect to the corresponding outer one I0 will be to set up a radially inwardly extending potential gradient in the generally annular intervening space. A sudden application of this relative potential will therefore deflect the beam a slight amount to make it follow a new course I6 and to strike radially inwardly to some circumferential point on the orbit Il, I8.

A corresponding or similar relative potential applied between the next set of elements II, Il may have a like deiiecting effect upon the beam, causing redeflection; and the simultaneous application of such potentials to elements I0, I0', I I, I I' may cause further deflection of the beam so as to strike orbit I9 peripherally. By applying additionally a strong enough potential between elements l2, i2', it appears clear that the beam may be caused to extend to the center of the screen, or even further, if so desired.

While the above described electrode arrangement may seem feasible, we vconsider it far too complex to be practical and, accordingly, prefer a more unitary construction, as shown in Fig. 2.- In the form shown, the outer electrode 20 of the structure is of generally conical form. A generally barrel-shaped concentric inner electrode ZI seems to be preferable as it will permit almost any degree of radial deflection that may be desired. Furthermore, if desired an electronintercepting disc-shaped plate electrode 22 may be provided, and this electrode may serve to limit the degree of radial deiiection. In the form shown, electrode 2i intercepts all electrons that are deflected so much that they otherwise would form images on the fluorescent screen on both sides of the center of the screen.

. The embodiment just describedmay nd particular application in radiogoniometric systems in which it is desired to obtain a veryv clear angular indication upon a cathode ray tube screen. A circular sweep will continuously rotate the beam about an outer orbit 23; and, if angular indication impulse energy is applied between members 2| and 2|), a sharply defined radial indication may be obtained. In other applications it may be desirable to show two angular indicationsv simultaneously on the screen. In such a case, by properly adjusting the potential between members 20 and 2| to a mean biasing gradient, a delecting potential in one polarity sense could serve to produce outward radial deflection momentarily, and a deflecting potential in the opposite polarity sense could serve to produce an inward momentary deection. Thus, two simultaneous indications could be obtained with ut most clarity on the screen; and there could be no confusion as to the identity of each, inasmuch as each indication would extend radially in an opposite sense with respect to the other.

As indicated above, certain features of the invention relate to electrode means whereby effectlve cathode ray tube magnication may be increased or decreased as desired. It is thus contemplated that electrode means may be made to adapt the applied signal indications to a showing utilizing the entire cathode ray screen to best advantage. To this end, concentric electrodes analogous to those above discussed in connection with the forms of Figs. 1 and 2 may be employed. However, for maximum deflecting efflciency it is preferred that these concentric electrodes be disposed as near as possible to the outlet of the electron gun.

Such an arrangement, utilizing electrostatic deflection throughout, is shown in Fig. 3. In the form shown the inner member 2li of the concentric electrode structure is of tear drop shape with the pointed end directed toward the electron gun 25. In order to locate the concentric ele-ctrodes 24, 26 as close to the origin of deflection as possible the lateral or sweep circuit deflection plates 21 are preferably of minimum size, that is, only large enough slightly to deflect the beam so as to avoid collision with the inner electrode 2d. It will be recalled by analogy of the form of electrode structure 24, 26 to those of the foregoing figures, that its function will be of a biasing nature, determining in effect a magnication or diminution of deiiections originating at the plates 21.

It is lbelieved that, since deflection plates 21 are so small, their accuracy of control may not be as great as desired. In this case, we propose the use of an additional set of relatively large plates 23 disposed in the same electrical sense or phase relation as plates 21, whereby a more strict and uniform control of sweeping may be assured. Although this additional set of plates 28 seems to us at present to have particular application in cooperation with set 21 for generating a circular sweep, it is clear that plates 28 may be energized Wholly independent of plates 21 and employed for other purposes.

In another` form of the invention it is possible to eliminate any need for two sets of deflecting plates, as in the case of Fig. 3, and at the saine time to maintain as high elciency and accuracy of the sweeping operation. This alternate form is shown in Fig. 4 in which the arrangement of elements is substantially that of Fig. 3 with the exception that magnetic means are used for deflection rather than electrostatic means. The tube of Fig. 4f thus comprises within an evacuated envelope 29, an electron gun 25 anda concentricl Y end 34 of the tube.

radial deflection structure 24', 26. 'I'he magnetic deection means for one axial sense is shown schematically to comprise a pair of coils 3l), 3|. For purposes of clarity the other pair of coils for deflection, say, in a sense perpendicular to that of coils 39, 3|, is omitted from the drawing. It is clear that by providing magnetic means for generating the circular sweeping energy, it is possible to arrange this circular deflection to take place at substantially the same axial position as the radial deflection, due to members 24', 2t. This arrangement is considered preferable inasmuch as members 24', 26' may extend into close proximity with the electron gun and circular sweeping may be performed simultaneously with radial deflection.

Fig. 4 additionally illustrates a preferred means or manner of supporting our novel electrode structure. Since electrons pass within member 25S', this electrode may be supported in a conventional manner by a relatively rigid lead in member 32. Appropriate support for the inner electrode 2 presents more of a problem, but this may `be accomplished by means of a rigid lead-in line 33, sealed to the center of the bulb or screen In order not to have potentials impressed on line 33 in any way interfere with the passage of electrons as controlled by members 2li and 2&3 and the magnetic coils, we propose that line 33 comprise a yconcentric line, as shown clearly in the broken-away portion. Control potentials may be supplied to electrode 24 by means of inner conductor 35. The outer conductor 36 may be electrically spaced from electrode 2li by means of an insulating washer 3l', and if it is given a potential equal to substantially that of the fluorescent screen, varying potentials on inner conductor 35 will have no el-Iect upon the electron lbeam except as applied to electrode 24.

In designing electrode structures in accordance with thev invention, it is considered preferable that the form of the outer electrode approximate the shape of average ilight of the electron beam.

. Thus, in Fig. 2, outer electrode 2li is substantially frusto-conicaL the electrode structure being spaced substantially from the electron gun or origin of deection (not shown); and in Fig. 4 electrode 26 is of the form of a generally inverse hyper-bola or parabola of revolution, since it is disposed near the origin of deiiection.

Although the invention has been described in particular detail in connection with the preferred forms illustrated, it is to be understood as not limited merely thereto.

What is claimed is:

1. In a cathode ray device, an electron gun, lateral deection means, a iluorescent screen, and concentric electrostatic deflection means for radial deflection, said last-mentioned means comprising an inner generally cylindrical member and an outer generally cylindrical member, said members diverging progressively with respect to each other toward said fluorescent screen.

2. In a cathode ray device, an electron gun, lateral deflection means, a iiuorescent screen, and concentric electrostatic deflection means for radial deiiection, said last-mentioned means comprising inner generally cylindrical electrode means and outer generally cylindrical electrode means, said inner electrode means and said outer electrode means diverging progressively with respect to each other toward said fluorescent screen.

3. A cathode ray device according to claim 1, in Which said inner member is of generally conical form having an apex in proximity to said electron gun.

4. A cathode ray device according to claim 1, in Which said lateral deflection means comprises coil means disposed about said device at substantially the same axial location as said concen- -tric deflection means.

5. In a cathode ray device having a generally cylindrical electrode disposed coaXially of the device, a support for said electrode comprising a relatively rigid lead-in secured to the center of one end of said device and to said electrode, said lead-in including a coaxial line having an inner conductor and an outer conductor, said inner conductor being conductively associated with said electrode, and said outer conductor being insulated from said electrode and providing a conducting shield for said inner conductor.

`6. A cathode ray device according to claim 1, further comprising a disc-shaped target electrode between said concentric means and said uorescent screen, said target electrode being coaxially disposed with respect to said concentric means.

'7. In a cathode ray device, an electron gun, a rst set of lateral deflection plates, a concentric electrode structure concentric with said gun and more remote from said gun than said first set of plates, and a second set of lateral deection plates more remote from said gun than said concentric structure,

8. A cathode ray device according to claim 'I in which said first and said second sets of deflection plates are similar in number and are connected in the same electrical phase relation.

HENRI G. BUSIGNIES. GEORGES PAUL CHEVIGN'Y. 

